As a conventional imaging device, one with a CMD (Charge Multiplying Detector)-CCD image pickup device including a charge multiplying means is known. In such an imaging device, due to deterioration, etc., of this device, a difference may occur between a multiplication factor that a user sets and an actual multiplication factor in an imaged multiplied image. Therefore, a method is known in which in such an imaging device, a first signal value imaged with pixels corresponding to a shading region of the CMD-CCD image pickup device and multiplied by a multiplication factor of 1 is stored, and further, a second signal value imaged with pixels corresponding to the shading region and multiplied by a predetermined multiplication factor is stored, and by dividing the second signal value by the first signal value, an actual multiplication factor is calculated (for example, refer to Patent Document 1).